Introduction
On 10 December 2016, a Boeing 737-400 aircraft, registration JY-JAQ, was operating a scheduled domestic passenger flight from Herat Airport (OAHR) to Kabul International Airport (OAKB) in Afghanistan. The flight, designated SFW 502, was conducted under a wet lease agreement with SAFI Airways. The aircraft departed Herat at 07:00 Z from runway 36, carrying 164 passengers, 7 operating crew members, and 2 engineers, totaling 173 persons on board.
Flight Details
As the flight approached Kabul, the crew received the automatic terminal information service (ATIS) at 07:45 Z, indicating normal weather with 6 kilometers visibility, a temperature of 7 degrees Celsius, and wind from 150 degrees at 7 knots. The aircraft was configured for landing with flaps set to 30 and an approach speed of 152 knots indicated airspeed (IAS), which was VREF plus 10 knots. Air traffic control cleared the flight for an ILS approach to runway 29 and vectored the aircraft via radar. The landing clearance was issued with wind reported at 190 degrees and 15 knots.
Landing and Incident
Shortly after touchdown on runway 29, the crew reported feeling vibrations. They applied brakes and deployed reverse thrust. The vibrations were followed by the aircraft rolling slightly to the right. The aircraft came to a full stop to the left of the runway centerline, resting on its left main landing gear and the right engine, with the nose landing gear elevated. The occurrence took place approximately 3,806 feet (1,160 meters) past the runway threshold.
Evacuation and Response
The pilot-in-command declared an emergency to air traffic control, and the cockpit crew initiated an evacuation from the left side of the aircraft. The evacuation was completed successfully, with no reported injuries. Kabul airport rescue and firefighting (RFF) personnel reached the aircraft and observed smoke emanating from the right side. They deployed foam on engine number 2. The aircraft sustained substantial damage due to the separation of the right main landing gear, which caused the aircraft to skid on the right engine cowlings. No injuries were reported among occupants or ground crew.
Investigation Findings
The Afghan Civil Aviation Authority (ACAA) interviewed the operating crew and conducted medical examinations, including alcohol and drug tests. The official investigation determined that the airplane occasionally experienced main landing gear shimmy. The most probable cause was that the struts were extended for a long period, causing the torsion link of the shimmy damper to remain in an extended vertical position, where the damper has less mechanical advantage. Contributing factors included the high altitude airport of 5,877 feet, an overly soft landing, a touchdown closure rate of 1 foot per second, and a high ground speed at touchdown of 178 knots resulting from a touchdown airspeed of 158 knots (VREF plus 16 knots).